Apparatus for feeding solids



March 7, 1961 c. R. DELAGRANGE ETAL 2,973,993

APPARATUS FOR FEEDING SOLIDS Filed March 25. 1958 form.

cyclones.

United States Patent vO 2,973,993 APPARATUS Fou rEEnlNG soLIDs'f Carl R. Delagrange, Ripplemead, and Gerard F. Meehan, Blacksburg, Va., assignors to Celanese Corporation of America, New York, N .Y., a corporation of Delaware Filed Mar.Y 2s, 195s, ser'. No. 723,740

16 claims. (c1. soz-'59) This invention relates to an apparatus =for feeding solid particles, and more particularly to an apparatus for feeding such particles into a zone which it is desired to isolate from the atmosphere.

In the operation of a plant for esfterifying wood pulp cellulose, sheets of the wood pulprare shredded and the fibers are pneumaticallyconveyed to a cyclone separator, the solids dropping down into an esterification vessel while the conveying air passes upwardly and out. Small wood pulp particles formed in the shredding, hereinafter referred to as cellulose dust, do not drop outof'the air stream in the cyclone separator but rather are carried out therewith.

It is an object of the invention to provide an apparatus for recovering this dust and converting it into a re-usable vIt is a further object of the invention to provide an vapparatus for positively feeding finely divided particles to a zone which it is desired to maintain isolated from the atmosphere.

Another object of the invention is to provide an apparatus for collecting Aairborne industrial dusts and fines, `f

compacting said fines into a plug and comminuting' said plug to form agglomerates of said fines.l f

Other objects and advantages of this invention will be apparent from the following description and claims.

Inaccordance with one aspect of the present invention, the dust-laden air is passed into a dust-precipitating device and the deposited dust is fed to a screw conveyor disposedin a line communicating with the conduit through kwhich air and shredded wood pulp are conveyed to the The screw conveyor compacts .the dustinto a plug which extends into the conveying conduity and which is broken'otf or abraded away by the material moving through the conduit, the particles into which the plug is subdivided being'suffciently large 'to drop out of the air stream upon reaching the cyclones. The invention will now be described more specifically vwith reference to the accompanying drawing,"wherein: Figgil is a schematic view, broken away `in part, of

' the over-all apparatus forV collecting, compressing and discharging industrial dusts,

Fig. 2 is a detailed view, broken away in part, ofthe screw compressor'of Fig. 1, t Fig. 3 is a vertical section through the compressor of Fig. 2,

Fig. 4 is a section taken on line 4 4 of Fig. 3.

Fig. 5 is a schematic view of another embodiment of compressing and discharging apparatus witheaportion bf the conveying-conduit broken away, f

Fig. 6 is a vertical section through the transport conduit, taken on line 6-6 of Fig. 5 and Fig. 7 is a plan view of a modified structure which can extend across the apertureaflording communication between the line housing the screw conveyor and the transport conduit.

Referring now more particularly to the drawing, in Fig. 1 there is shown a centrifugal blower 10 for pneu- ICC matically forwarding a subdivided material supplied at 11 to a conduit 12. The conveying gas and subdivided material, e.g. air and wood pulp, enter a cyclone separator `13 and the lar-gewood pulp particles `fall and drop through a valve 14 into a vessel such as a reactor` 15.

The conveying gas along with fine particles or dust leaver the separator and enter a .pipe 16. A slide gate damper 17 controls thevolume of air at a point .where only finely divided dust is handled inthe air, the large agglomerates having already been removed. An open-ended branch 18, provided with a conventional pivoted damper 19, communicates with pipe 16 and controls the flow of outside air into the pipe.

The dust laden air is pulled through pipe 16 by a blower V20 and is discharged into a high efficiency dust collector 21- of the mechanical or bag type which will remove small solid particles. Air leaves at the top of collector 21 and the dust drops downward into a line 22 provided along a portion of its inside with longitudinally extending brass ribs 23 to improve the feeding action of a screw 24 which rotates in line 22. As seen more clearly in Figs. 2, 3 and 4, screw 24 terminates shortV of the endV of line 22 and the dust is compacted beyond the screw into a plug 25. Y'

The inclined line 22 communicates across an aperture 26 with the transport conduit 12 through which the shredded wood pulp is pneumatically conveyed for usev aperture 26. Thefreeends of the fingers may lbe curved away from the screw conveyor.`

In operation, the plug 25 grows Yand moves toward aperture 26 as screw 24 rotates, the retaining fingers 30 providing resistance to compact the plug and thereby to form a gas-tight seal which prevents the gas within conlduit 12 from venting to the atmosphereby way of line 22. The lingers 30 are resilient and will bend away slightly, e.g. up to about 30 degrees, so as to permit the plug 25 to enter the conduit 12. As a result of the reduced influence of ngers30 on `the plug as it enters conduit 12 and as a result of theaction ofthe air and solids passing through Yconduit 12, the plug 25 partially falls away and is partially abraded away tobe carried along in conduit 12. The materialwhich breaks off from plug 25 comprises aggregates of many lineparlarge in size or cling to larger agglomerates so that they Ywill not pass out of separator 13 with the conveying gas.

In Fig. 5 there is shown a modified apparatus for forming and retaining a plug. Dust from collector 21 falls into a hopper 31 lcommunicating with a line 32 provided with longitudinal ribs 33, a shaft 34 extending through the line 32 and hopper 31 and being supported for rotation by conventional means (not shown). A helical thread 35 is connected with shaft 34, terminating short ofwhere line 32 communicates across an'aperture 36 with a transport conduit 37,*the latter being provided with top and bottom sight glasses 38; e

- The end of shaft 34 extends transversely through the wall of conduit 37. A shave-off 39 comprising a pair vof members bolted to eachother is secured to shaft 34 Patented Mar. 7, 1961 The screen 41 provides suicient resistance to compact the plug but the plug is subdivided in passing through the screen. Alternatively, threaded bolts projecting radially through the wall of the screw conveyor line can be employed to retain the plug and to aid -in its subdivision; The resistance which determines the degree of compaction can thus be adjusted by advancing the bolts further into the line or by partially withdrawing them from the line.

In practice it has been found that'particularlyw'good results are achieved when the screwconveyor discharges perpendicularly into the transport conduit and both are arranged in a horizontal plane.

While the invention has been described .with=reference to feeding Yof a wood pulp dust, it can-be used-withany tine material capable of being compacted to -a plug-which resists passage of gas therethrough. The plug thus forms a seal and permits operation without mixingbetween-the gas behind the screw and the gas within the `transport conduit, irrespective of which is nndergreater pressure.

It is to be understood that the foregoingdetailed description is merely given by way of illustration and that many variations may be made therein without departing from the spirit of our invention.

Having described our invention, what we desire to secure by Letters Patent is:

l. An apparatus for eicient feeding of subdivided material to a vessel comprising, in combination, means for pneumatically conveying said subdivided material to said vessel, means forseparating conveying gas together with fine particles of said subdivided material from other particles enteringsaid vessel, means for recovering said fine particles, means-for feedingV said recovered fine particles back to said conveyingmeans, and means for compacting said fine particles into a pluglprior to reaching saidconveying means` and for subdividing'said plug intoaggregates larger-than'said line particles;

2. An apparatus as set forth in claim- 1 wherein `said means for feeding said recovered fine particles comprises a screw conveyor, and said means for compacting-said line particles comprisesretaining means extending at least partially across the path of -advanceof said plug.

3. An apparatus as set-forth in clairn 2 wherein said screw conveyor andsaidV conveying means both extend in a horizontal plane.

4. An apparatus asV set forth in'claim 2 wherein said screw'conveyordischarges perpendicularly into said conveying means.

5. An apparatus as set forth in claim 2 wherein the retaining means comprises means for shaving said plug as said plug advances.

6. An apparatus assetlforth in claim 5 wherein said screw conveyor comprises a helical thread on a shaft which extends beyond said thread in the direction Vof advance of said particles, said shaving means being disposed on said shaft for rotation therewith.

7. An apparatusas set forth in claim 2 wherein the retaining means comprises a plurality of resilient lingers extending across thevoutlet of said line.

8. An apparatus as set forth in claim 2 wherein the retaining means comprises a grate through which said plug must pass, said plug thereby being subdivided into aggregates of said iine particles.

9. An apparatus as set forth in claim 2 wherein the inlet of said screw conveyor is higher than the outlet and said screw conveyor discharges into said conveying means at an acute angle.

10. The apparatus ofclaim 1 wherein said means for feeding said fine particles comprises a line having an inlet through which said line particles enter -and an outlet through which they leave, a screw conveyor disposed within said line for rotation to advance said tine particles from said inlet to said outlet, said screw conveyor terminating short of said outlet, and retaining means spaced from said screw conveyor-and impeding advance of said line particles beyond said screw conveyor, thereby causing said tine particles to compact into a plug, said retaining meanscomprisinga plurality of resilient fingers fixed at one end. and extendngacross the outlet of said line at their other ends.y

11. The apparatus of claim 1 wherein said means for feeding said fine particles comprises a line having an inlet through which said ne particles enter and an outlet through which they leave, a screw conveyor disposed within said line for rotation to advance said tine particles from said inlet to said outlet, said screw conveyor terminatingrshort of lsaid outlet, and retaining means spaced from. said screwconveyor and impeding advance of said fine particles beyond# said screw conveyor, thereby caus ing said tine .particles to compact into a plug, said retaining means comprising a grate through which said plug must pass, said plug thereby being subdivided into aggregates of said fine particles.

12. An apparatus for eicient feeding of subdivided material to a vessel comprising, in combination, a conduit for pneumatically conveying said subdivided material to said vessel, means for separating the conveying gas together with tine particles of said subdivided material carried along thereby from other particles entering said vessel, means for recovering said tine particles and for feeding them to a line which communicates'with said'conduit, a screw conveyor in said line terminating before said conduit, and retaining means impeding the advance of said particles from said line 4to said conduit, thereby cauSingsaidparticIes to compact into a plug.

13. An apparatus as set forth in claim 12 wherein the retaining means comprises a plurality of resilient ngers extending across the outlet of said line.

14. An apparatus as set forth in claim 12 wherein the retaining means comprises a grate through which said plug must pass, said plug thereby being subdivided into aggregates of said ne particles.

15. An apparatus as set forth in claim 12 wherein the retaining means comprises means lfor shaving said plug as said'plug advances.

16. An apparatus as set forth in claim 15 wherein said screw conveyor comprises a helical thread on a shaft which extends beyond said thread in the direction of advance of said particles, said shaving means being disposed on said shaft for rotation therewith.

References Cited in the le of this patent UNITED STATES PATENTS 1,468,966 Herington Sept. 25, 1923 1,495,479 Grindle May 27, 1924 1,505,188 Burns Aug. 19, 1924 1,889,176 Fletcher Nov. 29, 1932 2,127,693 McCanless Aug. 23, 1938 2,311,773 Patterson Feb. 23, `1943 2,321,015 Davis Iune 8, 1943 2,404,884 Pieper July 30, 1946 2,639,862` Watts May 26, 1953 FOREIGN PATENTS 393,280 Great Britain May30, 1933 

